For actuating the axial adjusting device, the driving motor is driven in a first direction of rotation. At least one of the discs may be coupled to the driving motor, via a reduction stage and rotated. The axially displaceable disc which is supported in turn on the axially supported disc is axially displaced against the resilient returning forces of the spring means.
The balls which contact end stops in the pairs of ball grooves and which, at the same time, are positioned in the deepest groove portions move to flatter groove portions as a result of the rotation of the discs relative to one another, as a result of which the discs are pressed apart.
If the driving motor is driven in the opposite direction or de-energized, the resilient returning forces of the spring means acting on the axially displaceable disc cause the latter to be pushed back. At least one rotatingly drivable disc is actively rotated back by the driving motor or via the effect of the balls in the ball grooves until the balls in their pairs of ball grooves stop against the end stops.
The balls in the ball grooves are subjected to high pressure forces so that ball damage (pittings) cannot be excluded. This may result in the balls being blocked and also in damage to the ball grooves.